This invention relates to header structure for a panel-type radiator and also to a method of making such header structure.
A panel-type radiator typically comprises a plurality of spaced-apart panels joined together at opposite ends of the radiator through two spaced-apart header structures that connect the panels in hydraulically-parallel relationship. Each of the panels is usually made of dished steel sheets welded together. These sheets are usually of a very thin-walled construction so as to facilitate the desired heat-transfer through the panel walls and also to facilitate their fabrication by a stamping and drawing operation.
Problems have been encountered in providing the header structures for joining the panels. Typically, these header structures are incorporated by welding or brazing operations, but the thin-walled construction of the panels has made it difficult to provide strong, leak-proof joints in the header structure. Sometimes the welding heat, particularly if derived from an arc, has melted through the thin sheets. Sometimes the welds or brazes are unduly porous. And sometimes the welds or brazes are not properly located in the finished structure to provide effective seals and strong joints. For several reasons it is especially difficult to properly locate the welds or brazes in a fully mechanized joining operation that relies upon an electric arc for heating. One reason is that the thin-walled sheets tend to distort in response to the heat of the arc, slightly changing the location of the interface that is being joined without a corresponding alteration in the path of the welding or brazing gun. Another reason is that sometimes slight bends or kinks develop in the free end of the welding wire used in gas metal-arc welding, and these tend to interfere with placement of the weld precisely in the desired location. And if the welding wire is of magnetic material, magnetic disturbances which affect the wire position can interfere with the desired precision in locating the weld.